ARINC 429

ARINC 429 is a technical standard specifying a data bus used primarily in avionics. Developed by Aeronautical Radio, Incorporated (ARINC), it defines how avionics equipment communicates with each other. It is a two-wire, data bus protocol considered a widely accepted standard for commercial and transport aircraft.

The protocol uses a self-clocking, self-synchronizing format with a data rate of either 12.5 or 100 kilobits per second. Data is transmitted in 32-bit words, with each word containing distinct fields including a label, source/destination identifier (SDI), data, and parity. The label identifies the type of data being transmitted.

ARINC 429 uses a single transmitter and up to twenty receivers on a single data bus, making it a broadcast protocol. The transmitter sends data which any of the receivers can listen to. However, a given receiver is typically configured to listen only for messages with specific labels.

The standard defines electrical characteristics, data formats, and protocol rules, promoting interoperability between different avionics systems from various manufacturers. Its relative simplicity and robustness have contributed to its longevity in the aviation industry. However, its limitations in bandwidth and the lack of a defined acknowledge signal are leading to increased adoption of newer standards in some applications.